Which of the given following method is ensured adequate safety by suitably restricting the stress in the materials (i. e. concrete and steel) induced by the expected working leads on the structures.

Question

Question

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JKSSB JE Civil Jal Shakti 6 Dec 2022 Official Paper (Shift 2)

Answer 1

Concept:

The design methods of reinforced cement concrete structures are as follows:

(A) Working stress method:

This method is based upon linear elastic theory or depends on the classical elastic theory.
This method ensured adequate safety by suitably restricting the stress in the materials induced by the expected working leads on the structures.
The basic assumption of linear elastic behavior is considered justifiable since the specified permissible stresses are kept well below the ultimate strength of the material.
The ratio of the yield stress of the steel reinforcement or the concrete cube strength to the corresponding permissible or working stress value is usually called a factor of safety.

(B) Ultimate load method:

This method is based on the ultimate strength of reinforced concrete at the ultimate load is obtained by enhancing the service load by some factor called load factor for giving a desired margin of safety.
The method is also referred to as the load factor method or the ultimate strength method.
In the ULM, the stress condition at the state of pending collapse of the structure is analyzed, thus using, the non-linear stress-strain curves of concrete and steel.
The safety measure in the design is obtained by the use of the proper load factor.

(C) Limit state method:

Limit states are the acceptable limits for the safety and serviceability requirements of the structure before failure occurs.
The design of structures by this method will thus ensure that they will not reach limit states and will not become unfit for the use for which they are intended.
It is worth mentioning that structures will not just fail or collapse by violating (exceeding) the limit states. Failure, therefore, implies that clearly defined limit states of structural usefulness have been exceeded.

Additional InformationLimit states are two types